The Syrian government has blamed Turkey, Qatar, and Saudi Arabia for a series of deadly explosions in two strongholds of President Bashar al-Assad’s regime on the Mediterranean coast.

The Foreign Ministry sent a letter to the United Nations, state media reported, saying the May 23 blasts in Tartus and Jableh were a “serious escalation by the extremist and malicious regimes of Riyadh, Ankara, and Doha," and were aimed at derailing peace efforts.

The Islamic State extremist group claimed responsibility for the attacks, in which a monitoring group said more than 145 people were killed.

Turkey, Qatar, and Saudi Arabia support various rebel forces in Syria.

Tartus and Jableh have been relatively insulated from the war raging in Syria, which has killed at least 270,000 people since March 2011.